In recent years, the underlying cause of sudden heart attacks (acute myocardial infarctions or AMI) has been the subject of much attention. The older prevailing theory of gradual occlusion of the coronary artery has been superseded by a new theory based on extensive histopathologic evidence that AMI is the result of a rupture in the coronary artery wall, specifically a rupture of a “vulnerable plaque.” A vulnerable plaque, also known as Thin-Capped Fibro-Artheroma (TCFA), is characterized by a thin fibrous cap covering a lipid pool located under the artery wall. Conventional x-ray based angiographic techniques can be used to detect narrowing of the artery. However, directly seeing the surface of the artery wall is essential to detect TCFA. Accordingly, a need therefore exists for a probe design that enables detecting and visualizing subsurface biological tissues and lipid pools.